Flux materials for heated solder placement and associated techniques and configurations

ABSTRACT

Embodiments of the present disclosure are directed towards flux materials for heated solder placement and associated techniques and configurations. In one embodiment, a method includes depositing a flux material on one or more pads of a package substrate, the flux material including a rosin material and a thixotropic agent and depositing one or more solder balls on the flux material disposed on the one or more pads, wherein depositing the one or more solder balls on the flux material is performed at a temperature greater than 80° C., and wherein the rosin material and the thixotropic agent are configured to resist softening at the temperature greater than 80° C. Other embodiments may be described and/or claimed.

FIELD

Embodiments of the present disclosure generally relate to the field ofintegrated circuits, and more particularly, to flux materials for heatedsolder placement and associated techniques and configurations.

BACKGROUND

An integrated circuit (IC) device such as, for example, a die may bemounted on a package substrate to form a package assembly. Solder ballsmay be attached to the package substrate to facilitate routing ofelectrical signals between the package substrate (e.g., and the die) andanother electrical component such as, for example, a motherboard. Insome cases, the package substrate may be warped as a result of adifference in coefficient of thermal expansion between materials of thepackage substrate and the mounted IC device. The warped package mayresult in misalignment of the solder ball placement during a ball attachprocess, which may lead to defective failures in forming the solder ballconnections to the package substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will be readily understood by the following detaileddescription in conjunction with the accompanying drawings. To facilitatethis description, like reference numerals designate like structuralelements. Embodiments are illustrated by way of example and not by wayof limitation in the figures of the accompanying drawings.

FIG. 1 schematically illustrates a cross-section side view of an exampleintegrated circuit (IC) package assembly, in accordance with someembodiments.

FIGS. 2A-C schematically illustrate an IC package assembly subsequent tovarious process operations.

FIG. 2A schematically illustrates an IC package assembly subsequent todepositing a flux material on one or more pads of the package substrate,in accordance with some embodiments.

FIG. 2B schematically illustrates an IC package assembly subsequent todepositing one or more solder balls on the flux material disposed on theone or more pads, in accordance with some embodiments.

FIG. 2C schematically illustrates an IC package assembly subsequent toperforming a solder reflow process to form a solder connection betweenthe one or more solder balls and the one or more pads of the packagesubstrate, in accordance with some embodiments.

FIG. 3 schematically illustrates a flow diagram for a method offabricating an IC package assembly, in accordance with some embodiments.

FIG. 4 schematically illustrates a computing device in accordance withone implementation of the invention.

DETAILED DESCRIPTION

Embodiments of the present disclosure describe flux materials for heatedsolder placement and associated techniques and configurations. In thefollowing description, various aspects of the illustrativeimplementations will be described using terms commonly employed by thoseskilled in the art to convey the substance of their work to othersskilled in the art. However, it will be apparent to those skilled in theart that the present invention may be practiced with only some of thedescribed aspects. For purposes of explanation, specific numbers,materials and configurations are set forth in order to provide athorough understanding of the illustrative implementations. However, itwill be apparent to one skilled in the art that the present inventionmay be practiced without the specific details. In other instances,well-known features are omitted or simplified in order not to obscurethe illustrative implementations.

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, wherein like numeralsdesignate like parts throughout, and in which is shown by way ofillustration embodiments in which the subject matter of the presentdisclosure may be practiced. It is to be understood that otherembodiments may be utilized and structural or logical changes may bemade without departing from the scope of the present disclosure.Therefore, the following detailed description is not to be taken in alimiting sense, and the scope of embodiments is defined by the appendedclaims and their equivalents.

For the purposes of the present disclosure, the phrase “A and/or B”means (A), (B), or (A and B). For the purposes of the presentdisclosure, the phrase “A, B, and/or C” means (A), (B), (C), (A and B),(A and C), (B and C), or (A, B and C).

The description may use perspective-based descriptions such astop/bottom, in/out, over/under, and the like. Such descriptions aremerely used to facilitate the discussion and are not intended torestrict the application of embodiments described herein to anyparticular orientation.

The description may use the phrases “in an embodiment,” or “inembodiments,” which may each refer to one or more of the same ordifferent embodiments. Furthermore, the terms “comprising,” “including,”“having,” and the like, as used with respect to embodiments of thepresent disclosure, are synonymous.

The term “coupled with,” along with its derivatives, may be used herein.“Coupled” may mean one or more of the following. “Coupled” may mean thattwo or more elements are in direct physical or electrical contact.However, “coupled” may also mean that two or more elements indirectlycontact each other, but yet still cooperate or interact with each other,and may mean that one or more other elements are coupled or connectedbetween the elements that are said to be coupled with each other. Theterm “directly coupled” may mean that two or elements are in directcontact.

In various embodiments, the phrase “a first layer formed, deposited, orotherwise disposed on a second layer,” may mean that the first layer isformed, deposited, or disposed over the second layer, and at least apart of the first layer may be in direct contact (e.g., direct physicaland/or electrical contact) or indirect contact (e.g., having one or moreother layers between the first layer and the second layer) with at leasta part of the second layer.

As used herein, the term “module” may refer to, be part of, or includean application Specific Integrated Circuit (ASIC), an electroniccircuit, a processor (shared, dedicated, or group) and/or memory(shared, dedicated, or group) that execute one or more software orfirmware programs, a combinational logic circuit, and/or other suitablecomponents that provide the described functionality.

FIG. 1 schematically illustrates a cross-section side view of an exampleintegrated circuit (IC) package assembly 100, in accordance with someembodiments. The IC package assembly 100 may include a package substrate104 having one or more dies (hereinafter “die 102”) mounted on thepackage substrate 104.

The die 102 can be attached to the package substrate 104 according to avariety of suitable configurations including, a flip-chip configuration,as depicted, or other configurations such as wirebonding and the like.In the flip-chip configuration, an active side of the die 102 isattached to a surface of the package substrate 104 using dieinterconnect structures 106 such as bumps, pillars, or other suitablestructures. The active side of the die 102 may have one or moretransistor devices formed thereon. The die 102 may represent a discretechip. The die 102 may be, include, or be a part of a processor, memory,or ASIC in some embodiments. In some embodiments, an encapsulant 108such as, for example, molding compound or underfill material may fullyor partially encapsulate the die 102.

Die interconnect structures 106 such as, for example, bumps may beconfigured to route electrical signals between the die 102 and thepackage substrate 104. In some embodiments, the die interconnectstructures 106 may be configured to route electrical signals such as,for example, input/output (I/O) signals and/or power or ground signalsassociated with the operation of the die 102.

The package substrate 104 may include electrical routing featuresconfigured to route electrical signals to or from the die 102. Theelectrical routing features may include, for example, traces (not shown)disposed on one or more surfaces of the package substrate 104 and/orinternal routing features such as, for example, trenches, vias or otherinterconnect structures (not shown) to route electrical signals throughthe package substrate 104. For example, in some embodiments, the packagesubstrate 104 may include electrical routing features such as die bondpads (not shown) configured to receive the die interconnect structures106 and route electrical signals between the die 102 and the packagesubstrate 104.

Package level interconnects 113 such as, for example, solder balls, maybe coupled to one or more pads 110 on the package substrate 104 tofurther route the electrical signals to another electrical device 120(e.g., motherboard or other circuit board). Although not shown, theother electrical device 120 may have corresponding pads or otherinterconnect structures to receive the solderable material 112. In someembodiments, the package substrate 104 is an epoxy-based laminatesubstrate having a core and/or build-up layers such as, for example, anAjinomoto Build-up Film (ABF) substrate. The package substrate 104 mayinclude other suitable types of substrates in other embodiments.

In some embodiments, the package level interconnects 113 may include asolderable material 112 such as, for example, one or more solder balls(e.g., solder balls 312 of FIG. 2B) that are coupled to the one or morepads 110 using a reflow process. A flux material 111 may be disposedbetween the solderable material 112 and the one or more pads 110 tofacilitate formation of a solder connection during the solder reflowprocess. The solder reflow process may form a solder connection betweenthe solderable material 112 and the one or more pads 110. In someembodiments, the solder connection of the package level interconnects113 may include intermetallic compound formed from materials of thesolderable material 112, the flux material 111 and/or the one or morepads 110. Although the flux material 111 is depicted with clean,straight lines, a boundary of the flux material 111 may be nonlinear ormay otherwise include other shapes or profiles in accordance withvarious embodiments.

In some embodiments, the package substrate 104 may be heated during aball attach process, referred to as a heated solder placement process,to attach the one or more solder balls (e.g., solderable material 112)to the one or more pads 110. The heated solder placement technique mayapply heat to the package substrate 104 during a ball attach process toreduce warpage of the package substrate 104 that may be caused bydifferences in Coefficient of Thermal Expansion (CTE) of material of theIC package assembly 100 and, thus, improve alignment and placement ofthe solder balls on target pads of the one or more pads 110. Theimproved alignment and placement of the solder balls may avoid defectivefailures or other yield loss associated with the package levelinterconnects 113.

According to various embodiments, the flux material 111 may beformulated to resist softening at elevated temperatures associated withthe heated solder placement. In some embodiments, the flux material 111is configured to resist softening at temperatures greater than about 80°C. and, in particular, at temperatures between 80° C. and 120° C. Forexample, the flux material 111 may be composed of materials that have asoftening point temperature that is greater than a temperature of theheated solder placement process. Such characteristic may provide a fluxmaterial 111 that does not bleed during the heated solder placement. Theflux material 111 may further retain a tackiness characteristic at theelevated temperature of the heated solder placement such that the solderballs adhere to the flux material 111 when placed or dropped on the fluxmaterial 111 during a ball attach process. Such characteristics of theflux material 111 may reduce defects such as high or missing balls,merged balls, bridging balls, and the like, which may be associated withother flux materials that may soften (e.g., bleed) or lose tackiness atelevated temperatures.

FIGS. 2A-C schematically illustrate an IC package assembly 200subsequent to various process operations. FIG. 2A schematicallyillustrates an IC package assembly 200 subsequent to depositing a fluxmaterial 211 on one or more pads 110 of the package substrate 104, inaccordance with some embodiments. In the depicted embodiment, the ICpackage assembly 200 is shown subsequent to depositing flux material onthe one or more pads 110 of the package substrate 104 using a stencilprinting method. For example, the flux material 211 may be pushedthrough one or more openings 252 of a stencil 250 adjacent to the one ormore pads 110. A squeegee 254 or analogous feature may be used to push(e.g., in the direction indicated by the arrows) the flux material 211through the one or more openings 252. The flux material 211 may bedeposited on the one or more pads 110 using other suitable depositiontechniques in other embodiments.

In some embodiments, the flux material 211 may be a formulationincluding one or more of a rosin, thixotropic agent, solvent, amine, andacid. The acid may include, for example, mono-, di-, and/ortri-carboxylic acids having between about 2 and 40 carbon atoms. Forexample, in some embodiments, the organic acid may include glycolicacid, oxalic acid, succinic acid, malonic acid, and the like, orcombinations thereof. The amine may include, for example, primary,secondary, and/or tertiary amines having between about 4 to 40 carbonatoms. For example, in some embodiments, the amine may include butylamine, diethylbutyl amine, dimethylhexyl amine, and the like, orcombinations thereof. The rosin may include, for example, naturallyoccurring or synthetically formulated rosin. The solvent may include anyof a wide variety of suitable solvents.

In some embodiments, the flux material 211 may further include a metalpowder (e.g., solder powder) such as, for example, tin, silver, orcopper to provide an electrically conductive solder paste. According tovarious embodiments, the flux material 211 may include a mixture of flux(e.g., rosin, thixotropic agent, solvent, amine, and acid) ranging fromabout 10% to 40% of the mixture by weight and metal powder ranging fromabout 60% to 90% of the mixture by weight. The flux material 211 may becombined with the metal powder in a mixer to form the solder paste. Insome embodiments, the flux material 211 is a low metal loading (LML)material.

Components of the flux material 211 may be composed of solid materialsthat resist softening at temperatures associated with heated solderplacement. For example, in some embodiments, the rosin and/or thethixotropic agent may resist softening at a temperature greater than 80°C. In some embodiments, the flux material 211 may resist softening at atemperature ranging between 80° C. and 120° C. The flux material 211 mayresist softening at lower or higher temperatures of a heated solderplacement process, in other embodiments.

A softening point temperature of components of the flux material 211 maybe increased by increasing a molecular weight of the components. Forexample, in some embodiments, the flux material 211 may be composed of arosin having a molecular weight greater than 300 and/or a thixotropicagent having a molecular weight greater than 500. The rosin and thethixotropic agent may have other values for molecular weight in otherembodiments.

In some embodiments, the flux material 211 may have a viscosity rangingfrom 1 pascal·second (Pa·s) to 300 Pa·s at a temperature of the heatedsolder placement and/or a thixotropic index (TI) ranging from 0.1 to 0.4at a temperature of the heated solder placement. The flux material 211may flow through the openings 252 of the stencil 250 and adhere to theone or more pads 110 without subsequent bleeding. In some embodiments,the flux material 211 may have a tackiness greater than 40 gram-force(gf) to facilitate adherence of one or more solder balls (e.g., one ormore solder balls 312 of FIG. 3) to the flux material 211 at the heatedsolder placement temperature (e.g., greater than 80° C.).

According to various embodiments, the rosin may include, for example, acombination of one or more rosin systems (e.g., rosin esters,hydrogenated rosin resins, dimerized rosin resins, modified rosinresins). In some embodiments, the flux (e.g., components of the fluxmaterial except the metal powder) may include from 10% to 80% rosin byweight. According to various embodiments, the thixotropic agent mayinclude, for example, agents for use in cross-linking systems, such as,for example, modified organic bentonites, amide waxes, and/or hydrolyzedcastor oils, or combinations thereof. In some embodiments, the flux(e.g., components of the flux material except the metal powder) mayinclude from 10% to 80% thixotropic agent by weight. The amount (weight%) of rosin and/or thixotropic agent in the flux may depend on amolecular weight (e.g., 350 to 450) and softening temperature (e.g.,150° C. to 190° C.) of the thixotropic agent. For example, a lowerpercentage of the thixotropic agent and/or rosin may be needed toelevate the softening temperature of the flux material 211 for heatedsolder placement for a higher molecular weight or higher softeningtemperature material.

FIG. 2B schematically illustrates the IC package assembly 200 subsequentto depositing one or more solder balls 312 on the flux material 211disposed on the one or more pads 110, in accordance with someembodiments. In the depicted embodiment, the IC package assembly 220 isshown subsequent to depositing one or more solder balls 312 using aheated solder placement process.

Heat may be applied to the package substrate 104 (e.g., in a range ofabout 80° C. to 120° C.) to reduce warpage of the package substrate and,thus, facilitate a more precise alignment of the solder balls 312relative to the one or more pads 110. The flux material 211 may beformulated to resist softening during the heated solder placement.

In some embodiments, the flux material 211 may have a tackiness greaterthan 40 gram-force (gf) at the heated solder placement temperature tofacilitate adherence of the one or more solder balls 312 to the fluxmaterial 211. For example, in the depicted embodiments, the solder balls312 may be dropped in the direction of the arrows through openings 352in a patterned grid 350 onto the flux material 211, as can be seen. Theflux material 211 may have the tackiness greater than 40 gf such thatthe dropped or placed balls adhere to the flux material 211 prior toperforming a solder reflow process as described in connection with FIG.2C. The solder balls 312 (e.g., or more generally the solderablematerial 112 of FIG. 1) may be deposited using other suitable techniquesin other embodiments.

FIG. 2C schematically illustrates the IC package assembly 200 subsequentto performing a solder reflow process to form a solder connectionbetween the one or more solder balls (e.g., solderable material 112) andthe one or more pads (e.g., pads 110) of the package substrate 104, inaccordance with some embodiments. According to various embodiments, thesolder reflow process may be performed by applying heat to the packagesubstrate to soften the solderable material 112 (e.g., solder balls 312of FIG. 2B) and metal powder, if any, of the flux material (e.g., fluxmaterial 211 of FIG. 2B) to form package level interconnects 113 thatinclude the flux material 111 that has undergone the reflow process. Insome embodiments, the reflow process forms a mechanical and electricalbond between the solderable material 112 and the one or more pads 110.

Although in the depicted embodiments of FIGS. 2A-C, the IC packageassembly 200 includes the die 102 attached to the package substrate 104,in other embodiments, the IC package assembly 200 may include thepackage substrate 104 without having the attached die 102 duringprocessing described in connection with FIGS. 2A-C. For example, the die102 may be attached subsequent to performing the solder reflow processto form the package level interconnects 113 of FIG. 2C in someembodiments.

FIG. 3 schematically illustrates a flow diagram for a method 300 offabricating an IC package assembly (e.g., the IC package assembly 100 ofFIG. 1), in accordance with some embodiments. The method 300 may comportwith embodiments described in connection with FIGS. 1-2C.

At 302, the method 300 may include providing a package substrate havingone or more pads (e.g., one or more pads 110 of FIG. 1). The one or morepads may be composed of an electrically conductive material such asmetal (e.g., copper) and may be configured to route I/O signals of a diethat is mounted or that will be mounted on the package substrate.

At 304, the method 300 may further include depositing a flux material(e.g., flux material 211 of FIG. 2) on the one or more pads. In someembodiments, the flux material may be deposited using a stencil printingtechnique. In other embodiments, the flux material may be depositedusing other suitable deposition techniques.

At 306, the method 300 may further include depositing a solderablematerial (e.g., one or more solder balls 312 of FIG. 2B) on the fluxmaterial using a heated solder placement process. The solderablematerial may be deposited using any suitable process including, forexample, techniques to drop or otherwise place solder balls on the fluxmaterial. The flux material may resist softening to avoid bleedingand/or have tackiness that promotes adhesion of solderable material tothe flux material during the heated solder placement.

At 308, the method 300 may further include performing a reflow processto form a solder connection between the solderable material and the oneor more pads. The solder connection may include the flux material insome embodiments. In some embodiments, package level interconnects(e.g., package level interconnects 113 of FIG. 1) are arranged in anarray on the package substrate at a pitch of less than about 0.3millimeters from one another.

At 310, the method 300 may further include coupling the packagesubstrate to a circuit board (e.g., electrical device 120 of FIG. 1)using the solderable material. The package substrate may be coupled tothe circuit board using any suitable technique including, for example,soldering techniques to couple the package level interconnects to thecircuit board.

Various operations are described as multiple discrete operations inturn, in a manner that is most helpful in understanding the claimedsubject matter. However, the order of description should not beconstrued as to imply that these operations are necessarily orderdependent. Embodiments of the present disclosure may be implemented intoa system using any suitable hardware and/or software to configure asdesired. FIG. 4 schematically illustrates a computing device 400 inaccordance with one implementation of the invention. The computingdevice 400 may house a board such as motherboard 402. The motherboard402 may include a number of components, including but not limited to aprocessor 404 and at least one communication chip 406. The processor 404may be physically and electrically coupled to the motherboard 402. Insome implementations, the at least one communication chip 406 may alsobe physically and electrically coupled to the motherboard 402. Infurther implementations, the communication chip 406 may be part of theprocessor 404.

Depending on its applications, computing device 400 may include othercomponents that may or may not be physically and electrically coupled tothe motherboard 402. These other components may include, but are notlimited to, volatile memory (e.g., DRAM), non-volatile memory (e.g.,ROM), flash memory, a graphics processor, a digital signal processor, acrypto processor, a chipset, an antenna, a display, a touchscreendisplay, a touchscreen controller, a battery, an audio codec, a videocodec, a power amplifier, a global positioning system (GPS) device, acompass, a Geiger counter, an accelerometer, a gyroscope, a speaker, acamera, and a mass storage device (such as hard disk drive, compact disk(CD), digital versatile disk (DVD), and so forth).

The communication chip 406 may enable wireless communications for thetransfer of data to and from the computing device 400. The term“wireless” and its derivatives may be used to describe circuits,devices, systems, methods, techniques, communications channels, etc.,that may communicate data through the use of modulated electromagneticradiation through a non-solid medium. The term does not imply that theassociated devices do not contain any wires, although in someembodiments they might not. The communication chip 406 may implement anyof a number of wireless standards or protocols, including but notlimited to Institute for Electrical and Electronic Engineers (IEEE)standards including Wi-Fi (IEEE 802.11 family), IEEE 802.16 standards(e.g., IEEE 802.16-2005 Amendment), Long-Term Evolution (LTE) projectalong with any amendments, updates, and/or revisions (e.g., advanced LTEproject, ultra mobile broadband (UMB) project (also referred to as“3GPP2”), etc.). IEEE 802.16 compatible BWA networks are generallyreferred to as WiMAX networks, an acronym that stands for WorldwideInteroperability for Microwave Access, which is a certification mark forproducts that pass conformity and interoperability tests for the IEEE802.16 standards. The communication chip 406 may operate in accordancewith a Global System for Mobile Communication (GSM), General PacketRadio Service (GPRS), Universal Mobile Telecommunications System (UMTS),High Speed Packet Access (HSPA), Evolved HSPA (E-HSPA), or LTE network.The communication chip 406 may operate in accordance with Enhanced Datafor GSM Evolution (EDGE), GSM EDGE Radio Access Network (GERAN),Universal Terrestrial Radio Access Network (UTRAN), or Evolved UTRAN(E-UTRAN). The communication chip 406 may operate in accordance withCode Division Multiple Access (CDMA), Time Division Multiple Access(TDMA), Digital Enhanced Cordless Telecommunications (DECT),Evolution-Data Optimized (EV-DO), derivatives thereof, as well as anyother wireless protocols that are designated as 3G, 4G, 5G, and beyond.The communication chip 406 may operate in accordance with other wirelessprotocols in other embodiments.

The computing device 400 may include a plurality of communication chips406. For instance, a first communication chip 406 may be dedicated toshorter range wireless communications such as Wi-Fi and Bluetooth and asecond communication chip 406 may be dedicated to longer range wirelesscommunications such as GPS, EDGE, GPRS, CDMA, WiMAX, LTE, Ev-DO, andothers.

The processor 404 of the computing device 400 may include a die (e.g.,die 102 of FIG. 1) in an IC package assembly (e.g., IC package assembly100 of FIG. 1) as described herein. The term “processor” may refer toany device or portion of a device that processes electronic data fromregisters and/or memory to transform that electronic data into otherelectronic data that may be stored in registers and/or memory.

The communication chip 406 may also include a die (e.g., die 102 ofFIG. 1) in an IC package assembly (e.g., IC package assembly 100 ofFIG. 1) as described herein. In further implementations, anothercomponent (e.g., memory device or other integrated circuit device)housed within the computing device 400 may contain a die (e.g., die 102of FIG. 1) in an IC package assembly (e.g., IC package assembly 100 ofFIG. 1) as described herein.

In various implementations, the computing device 400 may be a laptop, anetbook, a notebook, an ultrabook, a smartphone, a tablet, a personaldigital assistant (PDA), an ultra mobile PC, a mobile phone, a desktopcomputer, a server, a printer, a scanner, a monitor, a set-top box, anentertainment control unit, a digital camera, a portable music player,or a digital video recorder. In further implementations, the computingdevice 400 may be any other electronic device that processes data.

The above description of illustrated implementations of the invention,including what is described in the Abstract, is not intended to beexhaustive or to limit the invention to the precise forms disclosed.While specific implementations of, and examples for, the invention aredescribed herein for illustrative purposes, various equivalentmodifications are possible within the scope of the invention, as thoseskilled in the relevant art will recognize.

These modifications may be made to the invention in light of the abovedetailed description. The terms used in the following claims should notbe construed to limit the invention to the specific implementationsdisclosed in the specification and the claims. Rather, the scope of theinvention is to be determined entirely by the following claims, whichare to be construed in accordance with established doctrines of claiminterpretation.

What is claimed is:
 1. A method comprising: depositing a flux materialon one or more pads of a package substrate, the flux material includinga rosin material and a thixotropic agent; and depositing one or moresolder balls on the flux material disposed on the one or more pads,wherein depositing the one or more solder balls on the flux material isperformed at a temperature greater than 80° C.; wherein the rosinmaterial and the thixotropic agent are configured to resist softening atthe temperature greater than 80° C.; wherein the rosin material includesone or more of rosin ester, hydrogenated rosin resin, dimerized resin,or modified resin; wherein the thixotropic agent includes one or more ofan organic bentonite, amide wax, or hydrolyzed castor oil; wherein therosin material represents 10% to 80% by weight of the flux materialwithout a metal powder; and wherein the thixotropic agent represents 10%to 80% by weight of the flux material without the metal powder.
 2. Themethod of claim 1, wherein the flux material further includes a metalpowder, a solvent, an amine, and an acid.
 3. The method of claim 1,wherein: the rosin material has a molecular weight greater than 300; andthe thixotropic agent has a molecular weight greater than
 500. 4. Themethod of claim 1, wherein the flux material has a viscosity rangingfrom 1 pascal·second (Pa·s) to 300 Pa·s at the temperature greater than80° C. and a thixotropic index (TI) ranging from 0.1 to 0.4 at thetemperature greater than 80° C.
 5. The method of claim 1, whereindepositing the one or more solder balls is performed at a temperatureranging between 80° C. and 120° C. as part of a heated solder placementprocess to reduce warpage of the package substrate during deposition ofthe one or more solder balls.
 6. The method of claim 1, whereindepositing the flux material is performed by pushing the flux materialthrough openings in a stencil adjacent to the one or more pads.
 7. Themethod of claim 1, wherein depositing the one or more solder balls isperformed by dropping the one or more solder balls through a patternedgrid onto the flux material disposed on the one or more pads, and theflux material has a tackiness greater than 40 gram-force (gf) tofacilitate adherence of the one or more solder balls to the fluxmaterial at the temperature greater than 80° C.
 8. The method of claim1, further comprising: performing a reflow process to form a mechanicaland electrical bond between the one or more solder balls and the one ormore pads.
 9. A flux material for a heated solder placement process, theflux material comprising: a rosin material and a thixotropic agent thatis configured to resist softening at a temperature greater than 80° C.;wherein the rosin material includes one or more of rosin ester,hydrogenated rosin resin, dimerized resin, or modified resin; whereinthe thixotropic agent includes one or more of an organic bentonite,amide wax, or hydrolyzed castor oil; wherein the rosin materialrepresents 10% to 80% by weight of the flux material without a metalpowder; and wherein the thixotropic agent represents 10% to 80% byweight of the flux material without the metal powder.
 10. The fluxmaterial of claim 9, further comprising: a solvent; an amine; and anacid.
 11. The flux material of claim 9, wherein: the rosin material hasa molecular weight greater than 300; and the thixotropic agent has amolecular weight greater than
 500. 12. The flux material of claim 9,wherein the flux material is mixed with a metal powder to provide asolder paste that resists softening at the temperature greater than 80°C.
 13. The flux material of claim 9, wherein: the flux material has aviscosity ranging from 1 pascal·second (Pa·s) to 300 Pa·s at thetemperature greater than 80° C.; and the flux material has a thixotropicindex (TI) ranging from 0.1 to 0.4 at the temperature greater than 80°C.
 14. The flux material of claim 9, wherein the flux material has atackiness greater than 40 gram-force (gf) to facilitate adherence of oneor more solder balls to the flux material at the temperature greaterthan 80° C.
 15. The flux material of claim 9, wherein the flux materialresists softening at a temperature ranging between 80° C. and 120° C.16. A package assembly comprising: a package substrate having one ormore pads; a flux material disposed on the one or more pads, the fluxmaterial including a rosin material and a thixotropic agent that areconfigured to resist softening at a temperature greater than 80° C.; anda solderable material coupled to the one or more pads using the fluxmaterial; wherein the rosin material includes one or more of rosinester, hydrogenated rosin resin, dimerized resin, or modified resin;wherein the thixotropic agent includes one or more of an organicbentonite, amide wax, or hydrolyzed castor oil; wherein the rosinmaterial represents 10% to 80% by weight of the flux material without ametal powder; and wherein the thixotropic agent represents 10% to 80% byweight of the flux material without the metal powder.
 17. The packageassembly of claim 16, wherein the flux material further comprises asolvent, an amine, and an acid.
 18. The package assembly of claim 16,wherein: the rosin material has a molecular weight greater than 300; andthe thixotropic agent has a molecular weight greater than
 500. 19. Thepackage assembly of claim 16, wherein the flux material is a low metalloading material that resists softening at the temperature greater than80° C.
 20. The package assembly of claim 16, wherein the flux materialhas a viscosity ranging from 1 pascal·second (Pa·s) to 300 Pa·s at thetemperature greater than 80° C.
 21. The package assembly of claim 16,wherein the flux material has a thixotropic index (TI) ranging from 0.1to 0.4 at the temperature greater than 80° C.
 22. The package assemblyof claim 16, wherein the solderable material is electrically andmechanically coupled to the one or more pads and includes one or moresolder balls.
 23. The package assembly of claim 22, wherein the fluxmaterial has a tackiness greater than 40 gram-force (gf) to facilitateadherence of the one or more solder balls to the flux material at thetemperature greater than 80° C.
 24. The package assembly of claim 16,wherein the flux material resists softening during a heated solderplacement process performed at a temperature ranging from 80° C. and120° C. to place the solderable material on the flux material and reducewarpage of the package substrate during the heated solder placementprocess.
 25. The package assembly of claim 16, wherein the packageassembly is further coupled with a circuit board via the solderablematerial.
 26. The package assembly of claim 16, wherein the packageassembly is part of a laptop, a netbook, a notebook, an ultra book, asmartphone, a tablet, a personal digital assistant (PDA), an ultramobile PC, a mobile phone, a desktop computer, a server, a printer, ascanner, a monitor, a set-top box, an entertainment control unit, adigital camera, a portable music player, or a digital video recorder.